Do you have a Tractor Supply Outlet by you? My mom feeds 4Health from them because its not too expensive and comes in a big bag and is approved by me. It gets 4 out of 5 stars on dog food advisors website. I think its one of the better little-known foods around. I think its less than a dollar a pound.

Dogfoodanalysis is a good start but they miss a lot of controversial ingredients like menadione. They also miss the fact that by-products are often listed by scientific name to cover them up in the suppposed "high quality" foods. For instance: Blue Buffalo brands list Enterococcus faecium and hardly anybody knows this is the same as poop. Its a by-product often called animal digest. There are 5 other scientifically listed names on the ingredients that also make up whats in poop.

A decent quality food will probably help him fill out without looking for high fat. If he's been passed around a lot an isn't even neutered I doubt his previous owners cared enough to buy anything more than the cheapy grocery store foods.